高重频、高峰值功率纳秒铥光纤激光及脉冲时频控制技术研究

More diversified requirements are expected for 2μm pulsed lasers in latest industrial high-speed multiple materials processing and medical multiple tissues lasering. On the basis of traditional high-repetition-rate and high-peak-power laser system, it not only allows the users to customize the pulse widths, the repetition rates and the pulse profiles, but also allows the users to tune the laser center wavelength in a wide range. In this project, agile pulse control technique in time and frequency domain will be attempted in high-repetition-rate, high-peak-power nanosecond Tm-doped fiber laser for the first time. It will also give full play to the fiber laser system superiorities, such as the high broadband gain, high efficient thermal management and flexible machining. This project is expected to solve a series of essential scientific and technical problems in tunable thulium fiber laser system, including the generation of nanosecond pulse, the scaling up of peak power, and the pulse time-domain programming, which will further enhance the multi-dimensional and real-time manipulability of 2μm laser. The implementation of this project is of great theoretical and practical significance to study the time and frequency characteristics of tunable pulsed laser. Meanwhile, the project achievements should also be potential for much more applications, such as remote high spatial resolution LiDAR, infrared guiding, infrared countermeasure, pulsed laser beam spectral combining, mid-infrared laser pulse control, etc..

工业多材料高速加工场景与不同组织激光医疗的最新应用需求中，对2μm脉冲激光器的技术指标提出了更加多样化的要求，在传统高重频、高峰值功率激光输出基础上，要求允许客户自定义脉冲宽度、重复频率与脉冲波形，同时允许较大范围调节激光中心波长。本课题首次提出了高重频、高峰值功率纳秒铥光纤激光及脉冲时频控制技术的研究主题，充分发挥光纤激光系统的高宽带增益、高效热管理与柔性加工等优势。本课题将解决可调谐铥光纤激光系统中的纳秒脉冲激光实现、峰值功率提升与脉冲时域编程等系列关键科学与技术问题，进一步提升对2μm波段激光的多维度、实时在线操控能力。该课题实施对于可调谐脉冲激光时频特征研究具有重要的理论意义和实际应用价值，同时研究成果可以应用在长距离高空间分辨率LiDAR、红外导引、红外对抗、脉冲光谱合成以及中红外脉冲光源调控等更多场景中。

可调谐全光纤铥激光系统中的纳秒脉冲激光实现、峰值功率提升与脉冲时域编程等系列关键科学与技术问题，进一步提升对2μm波段激光的多维度、实时在线操控，有望在工业高速加工多材料、激光医疗不同组织作用等应用场景中得到实际应用。项目的具体研究内容包括：.1．对铥光纤激光器的带内泵浦源，及1.5 μm波段铒镱共掺光纤激光器，进行了广泛研究：比较不同泵浦源，以及不同波长的光纤布拉格光栅的增益变化；在DBR线性腔泵浦调制方面做了丰富实验研究，包括在500 Hz重复频率、占空比25%下的输出平均功率以及峰值功率差异性，以及在100 Hz重复频率、脉宽范围2-9 ms下的调制性能，总结了ASE引起光纤烧断的基本规律，最终实验证明可以获得19 W峰值功率稳定激光输出。.2．对2 μm波段掺铥光纤激光器的调谐、调制、脉冲放大等进行了实验研究：搭建了宽范围波长可调谐输出的环形腔种子源，实验获得中心波长1919.7 nm至1970 nm、可调范围超过50 nm的激光输出，在中心波长1923 nm处输出功率最高，达到138.9mW；通过外调制实现了100kHz至5MHz的任意脉冲激光输出；通过2级光纤放大，将最大平均功率提升至30W以上，将最大峰值功率提升至5.8kW。.3. 对项目研究的带内泵浦激光系统建立瞬态增益模型理论，指出下一步的课题研究方向与实验提升策略。